The rapid progress of wireless communication in recent years extends the information and communication services from digital homes to mobile lives. Different types of wireless communication technologies are widely applied to daily lives so that the demands in accessing internet resources through wireless devices also increase.
The current wireless communication technologies follow three major trends. First, wireless communication service providers are moving from providing pure voice service, such as GSM, to IP-based network service, including integrating voice, high speed data and multimedia streaming, such as GPRS and 3.5G. Second, broadband network communication providers are moving from providing local packet-switched internet service, such as ADSL, WiFi, to providing mobile communication/internet full service, such as DSRC, WiMAX. Third, information communication service system integrators are using information and communication technology (ICT) to provide new applications and services and IT-enabled service-based service integration technology and extend to the developments of all types of handheld mobile devices to offer real time streaming services in heterogeneous network environments.
The personal mobile service market is also expanding from three major directions, including first, the provision of real time multimedia entertainment on demand service, such as the user using portable device to request service from a remote server individually and ubiquitously and obtaining multimedia service, such as audiovisual replay and global positioning system (GPS); second, having the integration capability of multiple communication network interfaces, such as portable devices with different network communication interfaces able to switch in different environment to maintain optimal communication state; and third, the provision of seamless roaming in heterogeneous network environment, such as user of portable device able to obtain personal service at home, community or in mobility, towards the ubiquity and quality of service regardless of the change of network access.
Take the implementation of adaptive handover mechanism of service roaming in heterogeneous network as an example. U.S. Patent Publication No. 2007/0133472 disclosed a method of vertical handoff to predict the received signal strength (RSS) of a single system to realize the handoff in heterogeneous network. As shown in FIG. 1, the method of vertical handoff aims at the wireless network of a single small area and uses the least square (LS) algorithm, i.e., least square line 120, to predict the future RSS transition pattern 110 to achieve the handoff in heterogeneous network.
However, to achieve ubiquitous roaming in short, medium and long range heterogeneous network, one of the important issues is how to achieve seamless handover in different heterogeneous networks effectively and rapidly. Based on the integration service technology of mobile heterogeneous networks and targeting different heterogeneous network environments, it is important to integrate the channel estimation information to estimate the change of adaptive signal-tracking decay in addition to designing algorithm so as to improve the estimation handover correctness and reduce the system computation load.